Phase balancer



Aug. 28, 1923. 1,466,277

C}. LE (5. FORTESCUE PHASE BALANCER Filed April 4, 1919 WITNESSES: v INVENTOR fi C/ians LeG/Zrfescue.

ATTORNEY Patented Aug. 28, I923.

UNITED STATES PATENT OFFICE.

CHARLES G. FORTESCUE, OF PITTSBURGH, PENNSYLVANIA, 'ASSIGNOR TO WESTINGHOUSE ELECTRIC &'MANUF,ACTURINGOOMPANY, A CORPORATION OF PENNSYLVANIA.

PVHASE BALANGER.

Application filed April 4, 1919. Serial No.'287,609.

T 0 all whom it may concern:

Be it known that 1, CHARLES LE G. Fonrnscun, a subject of the King of Great Britain, and. a resident of Pittsburgh, in the county of Allegheny and State of Pennsylvania, have invented a new and useful Improvement in PhaseBalancers, of which the following is a specification.

My invention relates to polyphase balancing systems, and it has particular relation to balancing systems, having means for pro-- viding paths of very low impedance for the circulating currents which tend to flow in the field windings of machines from which unbalanced-load currents are drawn.

It has heretofore been a more or less usual practice to provide the stator of a machine with heavy windings, usually known as damper windings, in which currents would flow in such manner as to so reduce the flux set up by the unbalanced currents flowing in the armature of the machine that a path of low impedance would be offered to these currents. However. there are difficulties attending the provision of such damping windings and, moreover, the application thereof to a dynamo-electric machine does not always offer the desired symmetrical path to the flow of circulating 'currents.

I propose, therefore, to so wind an auxiliary dynamoelectric machine which furnishes exciting'currents to the field winding of the alternator, and so connect it thereto, that the machine shall perform substantially a double function, namely; it will furnish the required exciting current to the alternator and, at the same time, by the above-referred-to particular connection, it will offer a path of very low impedance to the circulating currents which flow in the field winding of the machine whenthat machine is furnishing unbalanced currents.

The manner in which I attain the above and other desirable objects will appear more fully hereinafter, and, for this purpose, reference may be had to the accompanying drawing, the single figure of which illustrates diagrammatically a dynamo-electric machine and an exciting machine connected theretofor the practice of my invention.

An alternating-current machine 1, having a stator winding 2 from which power is fed to a load through the mains 3-3, is provided with a rotating field winding 4. Slip rings 5-5 are connected to the winding-4 through suitable tap connections 66. For purposes of illustration, I will assume that the rotating field winding 4 is of the 2-pole type, and it will be observed, therefore, that there are twice as many equi-distant tapped points 6 as'there are poles. The reason for this particular relation will hereinafter appear and it will suffice, at this time, therefore, to point out "that, by the provision of the tapped'connections and the commensurate number of slip rings, I have established a 2-phase winding upon the arniiature of the dynamo-electric machine and, in addition, have substantially preserved its character as a 2-pole exciting winding.

An auxiliary dynamo-electric machine 7,

which I will hereinafter designate as the exciter, is preferably rigidly connected to, a

and rotates with, the machine 1 through the medium of a shaft 8. The GXCltGI' 7 comprises a distributed armature winding 9 connected. to commutator bars 10 and brushes l1--l1 bearing upon the commutator bars. ,-For purposes of illustration, I show a field winding 12 in simple diagram- .mat-ic relation to the armature winding'of the excitor; It will be understood, however, that any number of polesmay be established by this field winding, and my invenc rings 5 and the brushes 11.

Certain of the brushes 11 occupy such positions that they connect points of opposite potential'in the armature winding 9 of the exciting machine 7 and, under operating conditions, therefore, furnish exciting current to the rotating field winding l, while certain others of the brushes 11 connect points of substantially zero potential and are, therefore, in no way instrumental in at fecting the exciting current which the machine furnishes. They do, however, function in such manner, in connection with the equi-distant tapped connections 6, that :a symmetrical polyphase path of very low impedance is provided for the'fiow of those currents which are set up in the rotating Ill) field winding by reason cit the machine 1 furnishing unbalanced currents.

It is apparent, therefore, that I have combined in one n'ia'ehine an exciting function and a function which corresponds substantiall y to that which has heretofore been 0; tained by the use or" a damper winding upon a dynamo-electric machine. My method of oflering a path of perfect symmetry to the flow of the aforesaid circulating currents, by the simple connection of equi-distant tapped points to certain predetermined brushes upon the exciting machine, results in the accomplishm-ent of the dampin function with but slight increase in cost over the provision of dyi'ian'io-clectric machine and an exciter, neither being provided with a d amper wnding.

lVhile I have illustrated but one embodiment of my invention, it is apparent that many modifications therein may occur to those skilled in the art, and I desire, therefore, that my invention shall be construed broadly and be limited only by the scope of the appended claims, or by the disclosures of the prior art.

, I claim as my invention 1.

l. The combination with a synchronous, alternating-current machine having cymmetric-al damper windings, of an exciter therefor, and an arrangement by which all 0 l? the polyphase components of the damping current traverse symmetrical paths afforded by said exciter.

2. The combination with a alternating-current machine having symmetrical damper windings, of means for at- :tording symmetrical paths of low impedance for polyp-base currents induced in said damper windings, said means comprising an exei'ter machine having a plurality of symmetrically spaced brushes.

3. The combination with a. synchronous ')olyphase machine having symmetrical synchronous,

damper findings, of an exciter therefor. said' exciter including means for producing syms metrical, low-impedance paths through said exciter for polyphase currents indi'iced in said; damper windings.

4-. The combination with a synchronous, altemating-current machine having an exciting field winding, oian auxiliary dynamo-electric machine for furnishing exciting current thereto, said auxiliary Inaehine comprising av field member, an arma turehaving a distributed winding, a commutator member associated with said armature winding, and brushes bearing on said conunutator member, the number of said brushes being twice the number of poles in said auxiliary machine, and connections from each of said brushes to said exciting, field winding for producing symmetrical, low-impedance paths for polyphase current:-v induced in sai d exciting field windin The combination with a synchronous, alternating-current machine having an exciting field winding, said. winding having twice as many equi-spaced taps as there are poles on said machine, of an independent direct-current generator having two pairs of brushes, one of said pairs being located in the position of substantially maximum potential, and the other of said pairs being; loeated in the position of substantially zero potential, and connections from all O'l said brushes to said equi-spaced taps.

6. The combination. with a polyplu se line subject to unbalanced conditions, ot a dynanui-elcetric balancing machine having: primary windings and symmetri 'al polyphaue damper windings, said prii ary windings being connected to said polyphase line, and an exciter connected to said damper windings, said exci'rer including means for producing symmetrical, low-impedance paths through said exeiter for polyphase currents induced in said damper windings.

7 The combination with a. synchronous, alternating-current machine having polyphase damper wii'idings, of an auxiliary dyi'iamo-electric machine for furnishing exciting current thereto, said auxiliary ma chine comprising a. Hold member, an arma- 't-ure having a distributed winding, a conr mutator member assoc'ated with sai d armature winding, and means including a plurality o't brushes bearing on said commutator member for producing symmetrical, low-impedance paths tor polyphase currents induced. in said damper winding.

In testimony whereof, I have hereunto subscribed my name this 21st day of Mar. 1919.

CHARLES Ln G. FORTESCUE. 

